Inferior alveolar nerve (IAN) injury induces persistent ectopic pain which spreads to a wide area in the orofacial region. Its exact mechanism remains unclear. We investigated the involvement of nitric oxide (NO) in relation to ectopic orofacial pain caused by IAN transection (IANX). We assessed the changes in mechanical sensitivity of the whisker pad skin following IANX, neuronal nitric oxide synthase (nNOS) expression in the trigeminal ganglion (TG), and the functional significance of NO in relation to the mechanical allodynia following intra-TG administration of a chemical precursor to NO and selective nNOS inhibitors. IANX induced mechanical allodynia, which was diminished by intra-TG administration of selective nNOS inhibitors. NO metabolites and nNOS immunoreactive neurons innervating the lower lip were also increased in the TG. Intra-TG administration of nNOS substrate induced the mechanical allodynia. The present findings suggest that NO released from TG neurons regulates the excitability of TG neurons innervating the whisker pad skin, and the enhancement of TG neuronal excitability may underlie ectopic mechanical allodynia.

To recognize good mechanical properties and water-resistance of a dental resin, dimethacryloxyethyl-1,1,6,6-tetrahydro-perfluorohexamethylene- 1,6-dicarbamate (FDMHD) was newly synthesized. FDMHD initially was a white powder with m.p. 98.5-99.5°C. The copolymers of FDMHD and methyl methacrylate (MMA), FDMHD/MMA copolymers, were prepared to estimate the basic properties for dental resin materials. The compressive strength of FDMHD/MMA copolymers was almost the same compared with those of the copolymers of Bis-GMA or dimethacryloxyethyl-hexamethylene-1,6-carbamate (DMHD) and MMA. The bending, tensile, diametral tensile, impact strength and toughness of FDMHD/MMA copolymers containing 10.4 mol% FDMHD were higher than those of Bis-GMA/MMA copolymer, and the water sorption of FDMHD/MMA copolymers was lower than those of DMHD/MMA copolymers.

Occlusal disharmony is induced by various conditions such as the loss of teeth and inappropriate vertical dimension of crowns, bridges, or dentures. Occlusal disharmony sometimes causes indefinite complaint syndromes, which may be associated with astrocytic hypertrophy and the reduction of numbers of neuronal somata and their dendritic spines in the hippocampus. Microglia monitors the condition of neurons and responds to their degeneration accompanying with astrocytes. However, the effect of occlusal disharmony on the microglia has not yet been investigated. We artificially increased the occlusal vertical dimension by placing dental resin on the upper molars in mice and immunohistochemically investigated the effects of the increase in the vertical dimension on microglia of the hippocampal formation using an antibody against ionized calcium-binding adaptor molecule 1 (Iba-1), a marker protein for microglia. We measured the area occupied by Iba-1-immunoreactive microglia in the hippocampal CA1 region and dentate gyrus 1, 3, and 5 days after increasing the vertical dimension, and compared it with that of control mice. The hippocampal CA1 region contains vulnerable neurons and the dentate gyrus durable neurons. We found that the areas occupied by microglia in the hippocampal CA1 region increased, with the peak on the third day after increasing the vertical dimension, and it gradually declined by the fifth post-operative day. However, such an increase of the area occupied by microglia was not seen in the dentate gyrus. In conclusion, abnormal mastication may activate microglia in the area harboring vulnerable neurons, but not in the area harboring durable neurons.

Gum elastic bougie (GEB), a useful device for difficult airway management, has seldom been used for nasotracheal intubation. Among 632 patients undergoing dental procedures or oral surgery, GEB was used successfully in 16 patients in whom conventional nasal intubation had failed because of anatomical problems or maldirection of the tip of the tracheal tube. We recommend that GEB should be applied from the first attempt for nasal intubation in patients with difficult airways.

The aim of this study was to qualitatively evaluate a poly(lactic acid-co-glycolic acid-co-ε-caprolactone) (PLGC) membrane as a barrier for guided bone regeneration in the canine mandible and to compare it to a nonresorbable polytetrafluoroethylene (PTFE) membrane. Two wedge-shaped bone defects were created bilaterally in the mandibles of 12 beagle dogs. The bone defects in the left mandible were divided into three groups and treated as follows: PLGC membrane alone, PLGC membrane plus autogenous cortical bone chips, and titanium-reinforced expanded PTFE (TR-PTFE) membrane. The bone defects in the right mandible of each animal were left without membranes as a control. Computed tomography (CT) was performed at 3 and 6 months postoperative to evaluate bone regeneration. After a healing period of 6 months, the mandibles were removed en bloc for micro-CT and histologic analyses. CT analyses at 3 and 6 months showed that there was significantly more bone augmentation at all experimental sites than at the control sites. The volume of bone at defect sites covered with TR-PTFE was significantly greater than at defect sites covered with PLGC membrane with or without autogenous cortical bone. Micro-CT measurements showed that the volume of new bone formed at sites covered with TR-PTFE was significantly greater than at sites covered with PLGC membrane. However, the density of new bone was significantly higher at sites covered with PLGC membrane, with or without cortical bone, than at sites covered with TR-PTFE. Histologic analysis verified the presence of well-vascularized loose connective tissue in the pores of the PLGC membrane. Compared to TR-PTFE, the macroporous bioresorbable PLGC membrane did not significantly increase the amount of new bone in defect sites, but it facilitated the regeneration of mature bone.